This invention relates to a process for producing olefin polymers and to a high activity catalyst suitable for use in the process.
The present invention relates to a catalyst, a method for making the catalyst and a polymerization process for employing the catalyst. In accordance with another aspect, this invention relates to an improved olefin polymerization catalyst produced by reacting a vanadium halide compound, an organophosphorus compound, and a metal halide. In accordance with another aspect, this invention relates to a catalyst system comprising a vanadium-containing catalyst component and a cocatalyst comprising an organoaluminum compound. In accordance with a further aspect, this invention relates to the use of metal halides of periodic groups IIIA, IVA and VA in the formation of a vanadium-containing catalyst useful for the polymerization of olefins to form polymeric products having a broad molecular weight distribution. In accordance with still another aspect, this invention relates to the formation of ethylene polymers having a broad molecular weight distribution formed in the presence of a vanadium-containing catalyst produced as set forth herein.
It is old in the field of olefin polymerization to prepare solid polyolefins by employing catalyst systems comprising a transition metal compound and an organometallic cocatalyst. Until fairly recently most of such catalyst systems were relatively low in activity and as a result generally required the employment of a catalyst removal step in order to obtain a polymer having satisfactory properties. Recently, however, much research has been directed toward the discovery of catalyst systems that are so active that catalyst residues in resultant polymers are low and, thus, there is no need to employ the catalyst removal step. Such catalyst systems are obviously of significant commercial importance since they allow for appreciable reductions in the costs of producing such polymers.
The preparation of high activity ethylene polymerization catalysts based on vanadium are known. Ethylene polymers obtained from these catalysts are linear and saturated. The molecular weight distributions usually obtained, however, are broader than from other organometallic catalysts and to a certain extent, controllable. For some applications it is desirable to have still broader molecular weight distributions. One of the main reasons for broadening the molecular weight distribution of ethylene polymers is to obtain better environmental stress crack resistance (ESCR). It has been found that a simple modification in the preparation of vanadium-containing catalysts yields significantly broader molecular weight distributions with slight loss of activity.
The present invention is based upon the discovery of a way to produce a solid vanadium-containing catalyst capable of producing ethylene polymers exhibiting broad molecular weight distribution comprising producing the vanadium component with a metal halide and an organophosphorus compound.
Accordingly an object of this invention is to provide an improved polymerization catalyst.
A further object of this invention is to provide an improved process for the production of olefin polymers.
A further object of this invention is to provide a catalyst system adapted to produce polymers having a broad molecular weight distribution.
Other objects, aspects, as well as the several advantages of the invention will be apparent to those skilled in the art upon reading the specification and the appended claims.